M23 rebels claim they now control the Congolese city of Goma—an act Congo's government described as a 'declaration of war.'

In the aftermath of its withdrawal from Goma, the M23 suffered a series of heavy defeats at the hands of the Congolese army, which was backed by a multinational force. The M23 were subsequently expelled from the country. M23 fighters then agreed to be re-integrated into the army in return for promises that Tutsis would be protected.

Residents of eastern Congo's largest city of Goma greeted the arrival of Rwanda-backed rebels with trepidation on Monday, some staying indoors and others coming out to cheer in what one called a "show" of happiness.

A U.N. official says Congolese rebels and allied Rwandan forces have entered the outskirts of Goma and the airport in the key eastern city is no longer in use.

GOMA, Democratic Republic of Congo - Rwandan-backed rebels marched into east Congo's largest city Goma on Monday and troops from the east African neighbours exchanged fire over the border in the worst escalation of the long-running conflict for more than a decade.